Efforts are being made to develop an optical recording/reproducing method satisfying various requirements including a high density, a large capacity, a high access speed, and a high recording and reproducing speed together with a recording apparatus, a reproducing apparatus and a record medium used therein.
Among many sorts of optical recording/reproducing methods, a magneto-optical recording/reproducing method is most attractive because of a unique advantage that information can be recorded and then erased, and new information can be again recorded, which process can be repeated many times.
A magneto-optical disk (record medium) used in the magneto-optical recording/reproducing method has a magnetic layer composed of a layer or multiple layers for record storage. The magnetic layer used to be horizontal magnetic layer or layers (which are magnetized in parallel with the surface of layer) early disks. Then developed were perpendicular magnetic layer or layers having a high record density and a high signal intensity. The latter is used for almost 100% of magnetic layers at present. Such a magnetic layer is made for example of amorphous GdFe, GdCo, GdFeCo, TbFe, TbCo, TbFeCo, etc. The perpendicular magnetic layer generally has concentric tracks or spiral track, on which information is recorded. There are two types of tracks, i.e., explicit track and implicit track.